This application claims the priority of Korean Patent Application No. 10-2003-0057685 filed on Aug. 20, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to configuring addresses of mobile nodes present in a mobile network, and more particularly, to automatically configuring network addresses of mobile nodes participating in a mobile multi-hop network.
2. Description of the Related Art
A mobile ad hoc network provides a service to enable multi-hop based communications by connecting mobile terminals to one another by means of wireless links. Systems employing conventional wireless LAN based networks are constructed by connecting wired links to wireless links via access points. In such systems, since the coverage of the wireless links is not beyond the coverage within which the wireless links are directly connected to the access points, the access points can directly communicate with and control all terminal nodes. That is, mobile nodes can find access points and gain access to the Internet through connection with the found access points. In addition, a problem relating to allocation of an address system suitable to a current network, and the like can be overcome through direct communications among respective nodes.
However, in a mobile ad hoc network in which connection to access points is made using multi-hops to overcome limitations on the coverage of conventional networks, the access points cannot communicate directly with all terminal nodes. Under these circumstances, in order that each terminal node finds an access point and is allocated a network address from the access point for efficient access to the Internet, there is a need for a new mechanism that does not assume direct communication with access points.
In other words, when an access point for connection with the Internet is connected to an ad hoc based network, a mobile node has to be able to detect its own movement and find the access point, which relays the connection with the Internet, with a minimum network overload. In addition, the process of allocating the mobile node a network address by the access point and connecting the mobile node with the Internet using the allocated network address should be automatically and efficiently performed.
A conventional technique for performing such a process is shown in FIG. 1. In a conventional Bluetooth or wireless LAN based network, an access point (AP) 110 is connected to mobile nodes 111, 112 and 113, which are managed by the access point 110, within one hop. In order that the mobile nodes 111, 112 and 113 connected to the access point 100 via wireless links may be connected with the Internet 100, they utilize the access point 100 connected with the Internet using a wired or wireless link.
In such a configuration of a conventional network, all mobile terminal nodes can communicate directly with an access point. As for conventional techniques relating to such a configuration, International Publication Nos. WO 00/176154, WO 01/37497 and WO 02/23342 disclose unicast routing for an ad hoc network itself.
In the conventional technique shown in FIG. 1, since all the mobile terminal nodes 111, 112 and 113 can communicate directly with the access point 110, the access point can easily detect a mobile node 120 newly connected to the access point 110. If the new mobile node 120 is detected, this means that the mobile node 120 has moved. Then, the access point 110 confirms, based on a MAC address, whether the mobile node 120 belongs to a network under current management, and the access point 110 then relays connection of the mobile node 120 with the Internet 100. At this time, due to differences between address systems, there may occur a case where a new IP address should be configured for the mobile node 120. In this case, a user manually configures a new IP address in a network using a static IP, whereas the mobile node 120 is allocated a new IP address via a dynamic host configuration protocol (DHCP) in a network using a dynamic IP.
In the conventional technique, as shown in FIG. 1, it is assumed that the mobile terminal nodes 111, 112 and 113 and the access point 110 are connected directly to each other within one hop of the access point and a newly moved mobile terminal node also enters within one hop of the access point. In this case, the moved node can easily detect that there is a change in an access point responsible for its connection with the Internet. Further, since the moved node is located at the distance of one hop from a new access point, it is not necessary to find a route reaching the new access point for connection with the Internet. Moreover, as for the confirmation of an IP address, the user can manually allocate an IP address to the moved node, or the moved node can be easily allocated a new IP address using DHCP.
As described above, since the access point is connected, within only one hop, to all the mobile nodes managed by the access point in the conventional wireless LAN based network, the mobile nodes can efficiently find an access point for connection with the Internet and then be easily connected to the access point. In addition, problems relating to the allocation of an address system suitable for a current network, and the like can be easily solved.
However, in a mobile ad hoc network environment where mobile nodes are connected to one another through mobile multi-hops, only some of the mobile nodes can communicate directly with an access point within one hop and there are many cases where a new mobile node that has entered the network is not within one hop of the access point. Accordingly, when a mobile node has moved, it is difficult to detect that the connection of the mobile node to the access point for connection with the Internet has been changed. Further, there is a problem in that a route reaching a new access point should be found.
In addition, during the process of confirming an IP address, a mobile node that cannot communicate directly with an access point should receive an acknowledgement message through multi-hops of the ad hoc scheme. Accordingly, since the mobile node cannot use its own IP address until the use of the IP address is acknowledged by the access point, there is a problem in that it is difficult for the mobile node to transmit a message to the access point and receive a message from the access point.
As described above, in the mobile add hoc environment where mobile terminal nodes are connected to one another through mobile multi-hops, an access point cannot communicate directly with all the mobile terminal nodes. Therefore, when a mobile node moves, the whole processes by which the moved mobile node finds a route to an access point for connection with the Internet, confirms an address suitable for an address system of the access point and the mobile node is actually connected with the Internet through multi-hops.
Under the conditions where there is no topology information on a route and a destination, communications through multi-hops causes an increase in the number of broadcasts, resulting in the reduction in the overall efficiency of a network.